Slow wind belt in the quiet solar corona

Abstract

The slow solar wind belt in the quiet corona, observed with the Metis coronagraph on board Solar Orbiter on May 15, 2020, during the activity minimum of the cycle 24, in a field of view extending from 3.8 $R_{\odot }$ to 7.0 $R_{\odot }$, is formed by a slow and dense wind stream running along the coronal current sheet, accelerating in the radial direction and reaching at 6.8 $R_{\odot }$ a speed within 150 km s${}^{-1}$ and 190 km s${}^{-1}$, depending on the assumptions on the velocity distribution of the neutral hydrogen atoms in the coronal plasma. The slow stream is separated by thin regions of high velocity shear from faster streams, almost symmetric relative to the current sheet, with peak velocity within 175 km s${}^{-1}$ and 230 km s${}^{-1}$ at the same coronal level. The density-velocity structure of the slow wind zone is discussed in terms of the expansion factor of the open magnetic field lines that is known to be related to the speed of the quasi-steady solar wind, and in relation to the presence of a web of quasi separatrix layers, S-web, the potential sites of reconnection that release coronal plasma into the wind. The parameters characterizing the coronal magnetic field lines are derived from 3D MHD model calculations. The S-web is found to coincide with the latitudinal region where the slow wind is observed in the outer corona and is surrounded by thin layers of open field lines expanding in a non-monotonic way.

References in corpus (14)

• The Solar Orbiter mission -- Science overview
• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona
• Metis: the Solar Orbiter visible light and ultraviolet coronal imager
• Origins of the Ambient Solar Wind: Implications for Space Weather
• The temporal and spatial scales of density structures released in the slow solar wind during solar activity maximum
• First light observations of the solar wind in the outer corona with the Metis coronagraph
• Small-scale Flux Emergence, Coronal Hole Heating, and Flux-tube Expansion: A Hybrid Solar Wind Model
• The Color and Brightness of the F-Corona Inferred from the 2019 July 2 Total Solar Eclipse
• Exploring the Solar Wind from its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter - Parker Solar Probe Quadrature
• Direct observations of a complex coronal web driving highly structured slow solar wind
• The Solar Minimum Eclipse of 2019 July 2: II. The First Absolute Brightness Measurements and MHD Model Predictions of Fe X, XI and XIV out to 3.4 Rs
• Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy
• Effects of the chromospheric Lyα line profile shape on the determination of the solar wind HI outflow velocity using the Doppler dimming technique

Cited by in corpus (5)

• The Solar Minimum Eclipse of 2019 July 2. III. Inferring the Coronal $T_e$ with a Radiative Differential Emission Measure Inversion
• Particle monitoring capability of the Solar Orbiter Metis coronagraph through the increasing phase of solar cycle 25
• First detection of acoustic-like flux in the middle solar corona
• Constraints on the variable nature of the slow solar wind with the Wide-Field Imager on board the Parker Solar Probe
• Statistics of blob properties in two types of coronal streamers